1. Field
The disclosed subject matter relates to a lighting device for use in a vehicle light such as a stop lamp, an illumination lamp for interior illumination, and the like. In particular, the disclosed subject matter relates to a lighting device with lighter weight and improved outer appearance.
2. Description of the Related Art
FIG. 1 shows a conventional exemplary configuration of a lighting device 90 of this type. The lighting device 90 can include a substrate 91, LED chips 92 mounted on the substrate 91, and a transparent resin part 93 which covers the chips 92. The substrate 91 is formed of a conductive material such as a metal material having superior heat conductivity. The substrate 91 may be rectangular. The plurality of LED chips 92 is mounted in line in the lengthwise direction of the substrate 91. The transparent resin part 93 is substantially semi-cylindrical or barrel roof shaped.
In this case, a set including a red-light emitting LED chip, a green-light emitting LED chip, and a blue-light emitting LED chip is used as the LED chip 92, and are mounted on the substrate 91 such that they are in close proximity to each other. The surface of the transparent resin part 93 may be subjected to matte finish. In this lighting device 90, when light emitted from the respective LED chips pass through the transparent resin part 93, the red, green, and blue light beams are mixed with each other to provide pseudo white light.
Since the LED chips 92 are mounted on the heat-conductive substrate 91, even when they are mounted in close proximity to each other, the heat dissipation property of the lighting device may not deteriorate as compared to the case where lamp-type (cannonball shaped) LEDs are used. This can provide a brighter lighting device (see, for example, Japanese Patent Laid-Open Publication No. 2002-299697).
In this lighting device 90 configured as described above, the transparent resin part 93 with the semi-cylindrical shape is formed by filling the space close to the surfaces of the LED chips 92 with a transparent resin material. Therefore, a substantial amount of resin material is required. The resin material for use in this lighting device application is required to have a particular transparency, durability, water-resistance, and the like, which increases the material cost. This affects the entire cost for manufacturing the lighting device.
Furthermore, in this instance, the LED chips 92 are covered with the transparent resin part 93 under equal optical conditions across the emitting area of the device 90. Accordingly, it is difficult to provide special effects such as a light source displacement effect wherein one can see the light source as if it is displaced at different observation positions. Therefore, when turned on, the light source is not varied when observed at different positions. This means it has a monotonous appearance and is not decorative.